Intermittent Fasting Can Sharpen Your Brain and Help You Live Longer

The new year is a popular time to contemplate our relationship to calories, usually with the goal to reduce caloric intake. But in the last decade, our understanding of how the body deals with these units of energy has grown considerably. So here’s a look at what it means to eat a calorie in 2016.

You’ve probably heard that processed carbohydrates are now being viewed with the skepticism once reserved for fats, which are making a comeback. First thing in 2016, the USDA’s Dietary Guidelines Advisory committee reversed decades-long guidance and ditched caps on cholesterol and saturated fats.

In his 2008 book Good Calories, Bad Calories, Gary Taubes blew a hole in the idea that fat is the dietary boogeyman it’s been made out to be. He pointed out that the obesity epidemic coincides with the rise of a fat-fearing dietary paradigm and the accompanying boom in lowfat and nonfat processed foods that swapped fat for extra sugar.

That boom, which is supported by your tax dollars, is the real problem. Refined carbohydrates, Taubes explained, quickly convert into sugars, a process that starts in the mouth. And refined carbohydrates are everywhere, dominating most dishes on the American menu from pizza to macaroni and cheese. These arguments formed the basis for the many low-carb diets, such as South Beach and paleo, that have flourished in recent years.

Many others have added to Taubes’ core ideas, adding mechanisms for how sugar wreaks havoc on the human body and how easily carbohydrates become sugars.

Meanwhile, the timing of the meal has emerged as an important variable in the caloric equation. In addition to what we eat and how much, when we eat is also key. Martin Berkhan, author of the LeanGains blog, is primarily interested in adding muscle mass to his body, while keeping body fat to a minimum — and lifting the heaviest objects he can. Even if you don’t want to look like a ripped ant, his research on meal timing, the effects of which he’s demonstrated with his own body, are impressive.

Berkhan fasts for 16 hours a day, from evening until the following afternoon. Before breaking his fast, he exercises, including reps of 600-pound deadlifts. The workout is followed by eight hours of eating as much as he wants.

A nutritional consultant and personal trainer, Berkan cites research that growth hormone is naturally released in the early stages of a fast. Human growth hormone is known to promote fat breakdown and muscle gain, and Berkhan believes his daily fasting window is a powerful opportunity for the body to make the most of exercise.

It’s important to keep in mind that being skinny or ripped doesn’t mean one is healthy. And while Berkhan’s central, if not singular, priority is to maximize rippage and minimize fat, there is a growing body of research suggesting that the practice known as intermittent fasting, or IF, can significantly improve long-term health in many ways.

While IF has seen a recent rise in popularity — including a slew of books peddling variations on Berkhan's plan — the term has been around a while, first appearing in the science literature in a 1946 paper titled, "Apparent Prolongation of the Life Span of Rats by Intermittent Fasting." Since then, studies have demonstrated positive effects of IF on many other animals. And in humans, evidence suggests many benefits as well.

Mark Mattson is the chief of the Laboratory of Neurosciences at the National Institute on Aging and a professor of neuroscience at Johns Hopkins University. Like Berkhan, he pairs IF with regular exercise, though he leans more toward cardiovascular exercise, and is decidedly skinnier and less ripped than Berkhan. In a March 2014 Ted Talk, Mattson described some mechanisms by which he argues intermittent fasting may not only improve markers for cardiovascular health and blood sugar levels, but also improve brain function and help prevent neurodegenerative diseases like Alzheimer's and Parkinson's, as well as other age-related cognitive problems. Regular doses of moderate hunger, he argues, will make you sharper, regardless of your age.

A February 2015 paper in Rejuvenation Research detailed work by a University of Florida-based group that put volunteers on alternating feast and fast days. On fast days, they ate only 25 percent of a normal caloric intake. On feast days, they made up for it by eating 175 percent of normal. By dividing the feeding schedules like this between feast and famine, the team detected higher levels of a protective protein called SIRT 3 that correlates with increased lifespan in mice, as well as decreased blood insulin levels.

This feeding schedule also caused small but important bursts of free radicals; at high concentrations these reactive molecules can be very dangerous, but at low doses they are believed to have a cleansing effect.

“Fasting and calorie restriction and exercise activate a pathway called autophagy,” Mattson told the Columbia Chronicle, commenting on the Rejuvenation Research paper. Autophagy, or self-eating, “is a mechanism whereby cells remove garbage and that protects them from building up these damaging proteins. It also increases the production of neurotropic factors which we’ve seen lead to cognitive improvements in animals.”

One of the more surprising findings of the paper, and one which should be encouraging to aspiring fasters, was that sticking to this schedule wasn’t difficult for most participants. In fact, the majority of volunteers had a harder time meeting their 175 percent quota on feast days then staying below their 25 percent limit on fast days, according to co-author Michael Guo.

“We expected the fasting days to be more difficult but found it to be exactly the opposite,” he told the Columbia Chronicle. “On the feasting days, we had some trouble giving them enough calories.”

Intrigued by these ideas, and with a belly that isn’t aging particularly well, I began following the 16/8 eating schedule, which both Mattson and Berkhan endorse. I aim for last swallow by 10pm, and eating again by 2pm the next day. Since I’m not a breakfast eater, it wasn’t a dramatic shift, and felt like an exaggeration of what I was already doing. Still, while mornings have been relatively easy, cutting down on evening snacking has been a bit more challenging. And in the morning, I do splash some heavy cream into my otherwise zero cal coffee. Because, heavy cream. 

The routine also grooved with my workout schedule, because my belly is so weak I can only exercise when it's empty. The hunger pangs took a little getting used to, but I felt like I was functioning at a higher level. Granted, I had a lot more time on my hands without any cooking and cleaning and eating all morning long. I also feel noticeably sharper when I’m hungry. It’s almost a coffee-like buzz.

But maybe I’m just under the spell of Mattson’s conjecture, presented during his TED talk, for why a sharper mind might accompany hunger in an evolutionary context: "If you’re hungry and haven’t found food, you better figure out how to find food. You don’t want your brain to shut down if you’re hungry. And in fact, what we find in animals is that nerve cell circuits are more active."

In any case, I like this schedule. I feel like it works for me, and plan to continue, when possible.